1. Field of the Invention
This invention relates to speakers, and more particularly, but not exclusively, to flat panel loudspeakers used in public address systems.
2. Background
Loudspeakers today come in different configurations. A loudspeaker takes an electrical signal and translates it into physical vibrations to create sound waves.
A common loudspeaker configuration uses a driver (or exciter) that produces sound waves by rapidly pushing and pulling (piston action) a light weight, rigid cone or a diaphragm. The cone is usually made of paper, plastic or metal, and is attached to a suspension module. The “cone” shape is used to create a light weight but rigid mechanical structure, so that it can be effectively driven by the driver, exciter or motor. The suspension module, or surround, is a rim of flexible material (or specially contoured shape of the same cone material) that allows the cone to move, controlling the cone's maximum amplitude and is attached to the driver's metal frame, called the basket. The narrow end of the cone is connected to a voice coil. The voice coil is attached to the basket by a spider (suspension spring of the voice coil), a ring of flexible material. The spider holds the coil in position (within a magnetic gap), but allows it to move freely back and forth.
The foregoing conventional configuration has short comings in certain situations, for example, in an aircraft public addressing environment. A “cone diaphragm” type loudspeaker is tough to install in an aircraft interior environment. For example, the assembly height can be high (2 to 3 inches in general), heavy and also requires a speaker grill. In airplane interior, space and weight savings are very important. In addition, a cone speaker also has very narrow angle sound projection (very directional because it operates as a “horn speaker”) that does not provide adequate coverage for an aircraft interior. Therefore, a flat panel loudspeaker configuration is more suitable for aircraft public addressing (“PA”) systems.
Flat panel loudspeakers (may also be referred to herein as “speakers” or “flat panel speaker” throughout this application) are desirable in aircraft audio systems (for example, the aircraft PA system) because they can blend in easily with the interior of an aircraft. For example, no dissimilar appearance speaker grill is used that may ruin the uniform look of aircraft interior paneling, and also no holes are needed to install the speakers. Further more, flat panel speaker are low profile (approximately 1 inch in height), and very light weight.
The material used for a flat panel speaker and the method of installation of the speaker are very important. The present day airplanes use conventional fasteners, such as screws and nut plates, to affix the speakers on the airplane panel. This method of direct installation of the speaker on the interior aircraft panel has known to cause damage to the panel during installation. The aircraft panel may also suffer damage during maintenance or replacement of the speaker.
Another shortcoming of conventional flat panel speakers is that the drivers are not detachable. Hence, if anything goes wrong with the driver, the entire speaker assembly (in case of airplane interior application, this means replacement of entire piece of interior panel, which is very expensive) has to be discarded. This results in waste and also makes the installation/maintenance process difficult.
Therefore, there is a need for a flat panel speaker system, which provides optimum sound quality, is cost effective and is easy to install/maintain.